The difference between traditional drilling and spiral milling processing technology

The difference between traditional drilling and spiral milling processing technology
As a new hole processing method, spiral milling technology has the advantages of smooth cutting process, small cutting force on the tool and one-time processing to meet the precision requirements. This technology has become one of the hot spots and difficulties in material processing research at home and abroad. So, what is the difference between traditional drilling and spiral milling processing technology?

Traditional drilling technology

Traditional drilling processing has the following main characteristics:

First, in the traditional drilling process, the linear speed of the spindle center is 0, that is, the drill center does not participate in cutting, and the material in the central area of ​​the workpiece must rely entirely on the downward thrust of the drill to squeeze it out and remove it. Therefore, the Z-direction force borne by the drill is very large. When processing difficult-to-process materials such as titanium alloys, rapid wear and failure of the tool is inevitable.

Second, the traditional drilling process is a continuous cutting process. The blade is always in contact with the workpiece. The contact surface temperature is very high during cutting, and the thermal conductivity of titanium alloys is poor. The continuous cutting process causes the temperature to accumulate continuously, which also accelerates the wear and failure of the tool, resulting in a decrease in the quality of the processed surface.

Third, the chip removal method of traditional drilling is also a reason for tool failure. During the drilling process, the chips are discharged from the drill slot, and the chip removal speed is slow. The cutting heat is mainly taken away by the chips. When the cutting heat cannot be evacuated in time, a large amount of cutting heat remains on the workpiece and the tool, which will accelerate the wear and failure of the tool.

In addition, when the chips are in direct contact with the surface of the processed hole, the processed surface will be scratched. Obviously, this chip removal method affects the surface quality of the hole. Generally speaking, the quality of traditional drilling processing cannot meet the precision requirements of the aircraft manufacturing industry, and other processes must be relied on to ensure the surface quality of the hole, thereby reducing work efficiency and increasing processing costs. From the perspective of technical feasibility and economy, traditional drilling technology is no longer applicable to the aircraft manufacturing industry.

Spiral milling process

Compared with traditional drilling processing, spiral milling uses a completely different processing method. The spiral milling process is composed of two movements: the "rotation" of the spindle and the "revolution" of the spindle around the center of the hole. This special movement mode determines the advantages of spiral milling.

First, the trajectory of the tool center is a spiral line rather than a straight line, that is, the tool center no longer coincides with the center of the processed hole, which is an eccentric processing process. The diameter of the tool is different from the diameter of the hole, which breaks the limitation of one tool processing the same diameter hole in traditional drilling technology and realizes the processing of a series of diameter holes with a single diameter tool. This not only improves the processing efficiency, but also greatly reduces the number and types of stored tools, reducing the processing cost.

Second, the spiral milling process is an intermittent milling process, which is conducive to the heat dissipation of the tool, thereby reducing the risk of tool wear and failure due to temperature accumulation. More importantly, compared with traditional drilling, the spiral milling process has made great improvements in the use of coolant. The entire milling process can be cooled by micro-lubrication or even air cooling, which is a green and environmentally friendly process.

Third, the eccentric processing method allows enough space for chips to be discharged from the hole groove, and the chip removal method is no longer the main factor affecting the hole quality. It can be seen that this technology has broad development space and good market prospects, but as a new processing method, its processing mechanism needs further research and discussion.

Advantages of spiral milling

(1) Improve the quality of processed holes and tool life

Compared with traditional drilling technology, spiral milling significantly improves the quality and strength of holes; spiral milling is intermittent cutting, and the lower milling force makes the processed holes free of burrs; the tool diameter is smaller than the hole, so the chips can be discharged smoothly, which greatly reduces the roughness value of the hole surface; when processing composite materials, it eliminates the delamination, peeling, and low hole surface quality caused by tool tip blunting in traditional drilling.

The cutting ability of the center of traditional drilling tools is low, and it is easy to accumulate heat and wear quickly, and the tool life is generally low; spiral milling significantly improves the tool life due to the lower milling force.

(2) Shorten the development cycle and save processing costs.

When manufacturing aircraft or other heavy machines, the use of spiral milling technology will greatly shorten the development cycle and reduce costs.

The application of spiral milling technology can use the same tool to process holes of different diameters and complex shapes. Due to the superiority of its processing method, it can save traditional work such as countersinking and reaming. This means that the types and models of tools for processing holes will continue to decrease in the future. From the perspective of the entire development cycle, the use of spiral technology can reduce many processes (such as deburring, reaming, and clearing coolant for different holes after disassembly and assembly), greatly shortening the processing cycle.

(3) High degree of automation.

Achieving a higher degree of automation is also a way to reduce processing costs. Since the milling force of the spiral milling process is low, this technology can be applied to industrial robot devices. Since industrial robot devices are relatively weak and the axial force of traditional drilling is too large, traditional drilling cannot be applied to such devices.

(4) Promote the use of new materials.

The use of new materials in aircraft parts is an obvious development trend. New materials such as titanium alloys and composite materials have been widely used. The development and use of new materials requires suitable processing technology support. In terms of hole processing, research shows that spiral milling technology has significant advantages over traditional drilling technology.

The spiral milling process only needs one tool to process holes of different diameters and high quality, which not only reduces tool change time, but also saves finishing processes, greatly improving work efficiency. In view of the advantages of spiral milling technology, major companies, especially many companies in the aviation and mold industries, have begun to apply it to actual production. With the promotion and application of this technology, traditional drilling tools will gradually be eliminated, and new milling devices will appear more and more in machining workshops.